Rosemary extract can be used as a synthetic antioxidant to improve vegetable oil oxidative stability

• The oxidative stability of soybean, rice bran and cottonseed oil were tested.
• The oxidative stability of oils was tested using Rancimat and Schaal oven tests.
• Effect of rosemary extract on improving the stability of oils was evaluated.
• The use of rosemary extract as an effective alternative to synthetic antioxidants.

The protecting ability of rosemary extract as a plant-based antioxidant and an alternative to synthetic antioxidants against the oxidation of vegetable oils was investigated in the present study. The effect of rosemary extract on improving the oxidative stability of oils was evaluated using the Rancimat and Schaal oven tests. Oils with or without incorporation of rosemary extract or synthetic antioxidants were analyzed using the Rancimat method at 120 °C to determine their induction periods (IP). The changes in antioxidant capacity, total phenolic content, peroxide value, fatty acid composition, and tocopherol content were measured under the Schaal oven test during storage at 62 °C. The IP of oils incorporated with rosemary extract was significantly (p < 0.05) higher than blank oils and oils with synthetic antioxidants. The incorporation of rosemary extract into oils effectively prevented the oils by increasing the antioxidant capacity and total phenolic content, decreasing the peroxide value, and delaying the degradation of tocopherols and polyunsaturated fatty acids of oils. Results of this study suggested the potential use of rosemary extract as an effective alternative to synthetic antioxidants.